Operation control apparatus for compressor and method thereof

ABSTRACT

In an operation control apparatus and a method thereof, the compressor can be protected from overloading through a current control device instead of an OLP (Over Load Protector) and a PTC thermistor (Positive Temperature Coefficient thermistor). The operation control apparatus includes: a stroke estimated unit for estimating a stroke of the compressor on the basis of a current and a voltage applied to an interior motor of the compressor and a motor constant of the interior motor; a control unit for generating a control signal for varying a stroke of the compressor on the basis of the estimated stroke value and a preset stroke reference value; and a current control means being turned on/off so as to vary a stroke voltage applied to the interior motor of the compressor.

TECHNICAL FIELD

The present invention relates to a compressor and, particularly to anoperation control apparatus for a compressor used for a refrigerator anda method thereof.

BACKGROUND ART

Generally, in a compressor, particularly a reciprocating compressor,compression efficiency is higher than a general compressor since thereis no crankshaft for converting a rotational movement into a linearmovement and thus a friction loss is small.

In case that the reciprocating compressor is used for a refrigerator oran air conditioner, as varying a stroke voltage applied to thereciprocating compressor (interior motor of the compressor), being ableto vary a compression ratio, so that freezing capacity can becontrolled. The operation controlling apparatus for the reciprocatingcompressor will now be described with reference to FIG. 1.

FIG. 1 is a block diagram showing a configuration of the operationcontrol apparatus for the reciprocating compressor according to aconventional art.

As shown therein, the reciprocating compressor according to theconventional art includes an OLP (Over Load Protector) 11 electricallyconnected to a common terminal of a reciprocating compressor 12 andcutting off power applied to the interior motor (not shown) of thecompressor 12 when a temperature of the compressor 12 is high or anovercurrent flows into the interior motor of the compressor 12; and aPTC thermistor (Positive Temperature Coefficient thermistor) 13electrically connected to a sub-coil (not shown) of the compressor 12and initially protecting the compressor from being over-loaded bycutting off a current applied to the compressor 12 when a temperature ofthe compressor 12 increases at an initial stage of driving.

Herein, the OLP 11 is electrically connected with the compressor 12, andcuts off power applied to the interior motor of the compressor 12 when atemperature of the compressor 12 is high or an overcurrent flows intothe interior motor of the compressor. In addition, if an overload isgenerated at the compressor 12 due to a rapid increase of a temperaturegenerated when the compressor 12 starts initially, the PTC thermistorcuts off a current applied to the interior motor of the compressor so asto protect the compressor 12 from being over-loaded when the compressor12 initially starts.

However, in the reciprocating compressor used for a refrigeratoraccording to the conventional art, a stroke increases slowly so that anover current is not generated rapidly when the compressor initiallystarts. Accordingly, the PTC thermistor 13 is not required to beinstalled at the compressor, and a cost for producing the compressorincreases since the PTC thermistor 13 is installed at the compressor 12.

In addition, since the OLP 11 is installed at the compressor 12according to the conventional art, the operation control apparatus cannot be miniaturized by the size of a current device (not shown) in theOLP 11. Also, a production cost of the compressor 12 increases byinstalling the OLP 11 at the compressor 12.

DISCLOSURE OF THE INVENTION

Therefore, it is an object of the present invention to provide anoperation control apparatus for a compressor and its method capable ofprotecting the compressor from being over-loaded through a currentcontrol device instead of a PTC thermistor and an OLP.

It is another object of the present invention to provide an operationcontrol apparatus for a compressor and its method capable of reducing aproduction cost of the compressor by protecting the compressor frombeing over-loaded through a current control device instead of a PTCthermistor and an OLP.

To achieve the above objects, there is provided an operation controlapparatus for a compressor including: a stroke estimating unit forestimating a stroke of the compressor on the basis of a current and avoltage applied to an interior motor of the compressor and a motorconstant of the interior motor; a control unit for generating a controlsignal for varying a stroke of the compressor on the basis of theestimated stroke value and a stroke reference value; and a currentcontrol means for varying a stroke voltage applied to the interior motorof the compressor by being turned on/off according to the controlsignal.

To achieve the above objects, there is also provided an operationcontrol apparatus for a compressor including: a detecting means fordetecting a current and a voltage applied to the compressor; a storingmeans presetting a standard current value for preventing an overcurrentgenerated when the compressor initially starts, and storing the setstandard current value; a comparing means for comparing the detectedcurrent value and the standard current value, and outputting a comparingsignal corresponding to the comparing result; and a control means forcutting off a current applied to the compressor by turning off thecurrent control means installed at the compressor by the comparingsignal, or controlling a stroke voltage applied to the compressor byturning on/off the current control means at a certain period.

To achieve the above objects, there is also provided a method forcontrolling an operation of a compressor including the steps of:detecting a current and a voltage applied to the compressor; estimatinga stroke of the compressor on the basis of the detected values of acurrent and a voltage and a motor constant of an interior motor of thecompressor; and increasing a voltage applied to the compressor bylengthening an on/off period of the current control means installed atthe compressor when the estimated stroke value is smaller than a presetstroke reference value, and decreasing a voltage applied to thecompressor by shortening the on/off period of the current control meanswhen the estimated stroke value is greater than the stroke referencevalue.

To achieve the above objects, there is provided a method for controllingan operation of a compressor including the steps of: detecting a currentapplied to the compressor; comparing the detected current value and apreset standard current value; cutting off a current applied to thecompressor by turning off a current control means installed at thecompressor when the detected current value is greater than the standardcurrent value; and, when the detected current value is the same as orsmaller than the standard current value, estimating a stroke of thecompressor, and controlling a stroke voltage applied to the compressorby turning on/off the current control means at a certain period on thebasis of the estimated value and a preset stroke reference value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration of an operationcontrol apparatus for a reciprocating compressor according to theconventional art;

FIG. 2 is a block diagram showing a configuration of an operationcontrol apparatus for a reciprocating compressor according to a firstembodiment of the present invention;

FIG. 3 is a flow chart showing an operation order of an operationcontrol apparatus for a reciprocating compressor according to a firstembodiment of the present invention;

FIG. 4 is a block diagram showing a configuration of an operationcontrol apparatus for a reciprocating compressor according to a secondembodiment of the present invention; and

FIG. 5 is a flow chart showing an operation order of an operationcontrol apparatus for a reciprocating compressor according to a secondembodiment of the present invention.

MODES FOR CARRYING OUT THE PREFERRED EMBODIMENTS

Hereinafter, a preferred embodiment of an operation control apparatusfor a compressor and its method capable of preventing damage to acompressor, which is caused by the overload (overcurrent), by using acurrent control device without using the OLP and the PTC thermistor,will now be described with reference to FIGS. 2 to 5. Herein, thecompressor is installed at a refrigerator.

FIG. 2 is a block diagram showing a configuration of the operationcontrol apparatus for the reciprocating compressor according to a firstembodiment of the present invention. That is, the amount of currentsapplied to the compressor 200 is controlled through the current controldevice (triac, Tr) installed at the compressor 200 without using the OLP(Over Load Protector) and the PTC thermistor. Also, when the compressorinitially starts, a stroke of the compressor is estimated to slowlyincrease the stroke of the compressor, and varies the stroke of thecompressor by turning on/off the current control device (Tr) at acertain period on the basis of the estimated stroke.

As shown therein, the operation control apparatus for the reciprocatingcompressor includes: a voltage detecting unit 102 for detecting avoltage applied to an interior motor (not shown) of the reciprocatingcompressor 200 when the reciprocating compressor is operated; a currentdetecting unit 101 for detecting a current applied to the interior motorof the compressor when the compressor 200 is operated; a strokeestimating unit 103 for estimating a stroke of the compressor on thebasis of a voltage value detected from the voltage detecting unit 102, acurrent value detected from the current detecting unit 101 and a motorconstant of the interior motor of the compressor; a control unit 104 forcomparing the estimated stroke value and a preset stroke referencevalue, and generating a control signal on the basis of the comparingresult; and a power supply unit 105 for on-off controlling an interiorcurrent control device (e.g. Triac, Tr) according to the control signalgenerated from the control unit 104 and thus varying a stroke voltagesupplied to the interior motor of the reciprocating compressor 200.Herein, a resistor (R) in the power supply unit 105 is installed tomeasure a current applied to the compressor 200. In addition, thereciprocating compressor 200 varies an inner stroke by receiving astroke voltage provided to the interior motor according to the strokereference value set by a user, and vertically moves a piston (not shown)in the compressor.

Hereinafter, an operation of the operation control apparatus for thereciprocating compressor according to the first embodiment of thepresent invention will now be described in detail with reference to FIG.3.

First, the reciprocating compressor 200 varies the stroke by receiving avoltage supplied to the interior motor in depending on the strokereference value set by a user, and thus vertically moves the piston.Herein, the stroke means a moving distance of the piston in thereciprocating compressor 200 while the piston reciprocally moves.

A turn-on period of the current control device of the power supply unit105 is lengthened by a control signal outputted from the control unit104. An alternating current power is supplied to the reciprocatingcompressor 200 due to the lengthened turn-on period, and thus thereciprocating compressor 200 is driven. At this time the voltagedetecting unit 102 and the current detecting unit 101 detect a voltageand a current applied to the reciprocating compressor 200 respectively,and then output the detected value of the voltage and the current to thestroke estimating unit 103 (S11). The stroke estimating unit 103estimates a stroke of the compressor 200 on the basis of the voltagevalue detected from the voltage detecting unit 102, the current valuedetected from the current detecting unit 101 and a motor constant of theinterior motor, and outputs the estimated stroke value to the controlunit 104 (S12).

The control unit 104 compares the estimated stroke value and the presetstroke reference value, and outputs a control signal on the basis of thecomparing result (S13). That is, when the estimated stroke value issmaller than the stroke reference value, the control unit 104 outputs acontrol signal for lengthening the turn-on period of the Tr to the Tr ofthe power supply unit 104 and thus increases a stroke voltage suppliedto the reciprocating compressor 200. On the other hand, when theestimated stroke value is greater than the stroke reference value, thecontrol unit 104 outputs a control signal for shortening the turn-onperiod of the Tr to the Tr of the power supply unit 105 and thusdecreases a stroke voltage supplied to the reciprocating compressor 200(S14, S15).

Herein, the current control device (Tr) is installed instead of an OLP,and is on/off switched by the control signal of the control unit 104 soas to be able to vary a stroke of the compressor 200, or cut off acurrent applied to the interior motor of the compressor. In addition,preferably, one of a triac, GTP transistor (gate turn-off transistor ora gate turn-off thyristor), an IGBT (Insulated Gate bipolar Transistor)a bipolar transistor and a relay is used as the current control device.

Hereinafter, a configuration of an operation control apparatus for thereciprocating compressor according to a second embodiment of the presentinvention will now be described in detail with reference to FIG. 4.

FIG. 4 is a block diagram showing the configuration of the operationcontrol apparatus for the reciprocating compressor according to thesecond embodiment of the present invention. That is, in the operationcontrol apparatus for the reciprocating compressor according to thesecond embodiment of the present invention, a current control device(Tr) instead of the OLP and the PTC thermistor is installed at thecompressor 200, and the amount of currents applied to the interior motorof the compressor 200 is controlled through the current control device(Tr). Also, in the operation control apparatus for the reciprocatingcompressor according to the second embodiment of the present invention,in order to protect the compressor 200 from an overcurrent generatedwhen the compressor 200 initially starts, a current applied to thecompressor 200 and a preset standard current is compared. Then,according to the comparing result, a current applied to the interiormotor of the compressor 200 is cut off by turning off the currentcontrol device (Tr) or a stroke of the compressor is controlled byturning on/off the current control device (Tr) at a certain period.

As shown in FIG. 4, the operation control apparatus for thereciprocating compressor according to the second embodiment of thepresent invention includes: a voltage detecting unit 102 for detecting avoltage applied to an interior motor (not shown) of the reciprocatingcompressor when the reciprocating compressor 200 is operated; a currentdetecting unit 101 for detecting a current applied to the interior motorof the compressor 200 when the compressor 200 is operated; a strokeestimating unit 103 for estimating a stroke of the compressor on thebasis of a voltage value detected from the voltage detecting unit 102, acurrent value detected from the current detecting unit 101 and a motorconstant of the interior motor of the compressor; a standard currentvalue storing unit 106 for storing a preset standard current value tocut off an overcurrent generated when the compressor initially starts; acomparing unit 107 for comparing the current value detected from thecurrent detecting unit 101 and the standard current value previouslystored at the standard current value storing unit 106, and outputting acomparing signal corresponding to the comparing result; a control unit104 for generating a cut-off signal for cutting off a current applied tothe interior motor of the compressor on the basis of the comparingsignal, or comparing the estimated stroke value and the stroke referencevalue, and then generating a control signal on the basis of thecomparing result; and a power supply unit 105 for cutting off a currentapplied to the interior motor of the compressor 200 by turning off theinner current control device by the cut-off signal generated from thecontrol unit 104, or controlling a stroke voltage applied to theinterior motor of the reciprocating compressor 200 by on-off controllingthe current control device (Tr) on the basis of the control signal.

Herein, when the current value detected from the current detecting unit101 is greater than the standard current value previously stored at thestandard current value storing unit 106, the control unit 104 generatesa cut-off signal and outputs the generated cut-off signal to the currentcontrol device (Tr) in the power supply unit 105. At this time, thecurrent control device (Tr) is turned off based on the cut-off signal soas to cut off a current applied to the interior motor of the compressor.

On the other hand, when the current value detected from the currentdetecting unit 101 is the same as or smaller than the standard currentvalue previously stored at the standard current value storing unit 106,the control unit 104 generates a control signal and outputs thegenerated control signal to the current control device (Tr) in the powersupply unit 105. That is, when the current value detected from thecurrent detecting unit is the same as or smaller than the standardcurrent value previously stored at the standard current value storingunit 106, the control unit 104 controls the turn-on period of the Tr inthe power supply unit 105 and thus varies a stroke voltage applied tothe interior motor of the compressor 200.

Hereinafter, an operation of the operation control apparatus for thereciprocating compressor according to a second embodiment of the presentinvention will now be described in detail with reference to FIG. 5.

FIG. 5 is a flow chart showing an operation order of an operationcontrol apparatus for a reciprocating compressor according to the secondembodiment of the present invention.

First, when the compressor 200 is operated, the current detecting unit101 detects a current applied to the interior motor of the compressor200 at a real time, and outputs the detected current value to the strokeestimating unit 103 and the comparing unit 107. At this time, when thecompressor 200 is operated, the voltage detecting unit 102 detects avoltage applied to the interior motor of the compressor 200 at a realtime, and outputs the detected voltage value to the stroke estimatingunit 103 (S21).

The stroke estimating unit 103 estimates a stroke of the compressor 200on the basis of the detected voltage value, the detected current valueand the motor constant of the interior motor, and outputs the estimatedvalue (the estimated stroke value) to the control unit 104.

The comparing unit 107 compares the standard current value previouslystored at the standard current value storing unit 106 and the currentvalue detected from the current detecting unit 101, and outputs a signalcorresponding to the comparing result to the control unit 104.

When the current value detected from the current detecting unit 101 isgreater than the standard current value, the control unit 104 generatesa cut-off signal, and outputs the generated cut-off signal to thecurrent control device (Tr) (S22). At this time, the current controldevice (Tr) is turned off based on the cut-off signal so as to cut off acurrent applied to the interior motor of the compressor (S23, S24).

On the other hand, when the current value detected from the currentdetecting unit 102 is the same as or smaller than the standard currentvalue, the control unit 104 generates a control signal, and outputs thegenerated control signal to the current control device. That is, whenthe current value detected from the current detecting unit 102 is thesame as or smaller than the stand current value, and the estimatedstroke value is smaller than the stroke reference value, the controlunit 104 outputs a control signal for lengthening a turn-on period ofthe Tr to the Tr and thus increases a stroke voltage supplied to theinterior motor of the reciprocating compressor 200. On the other hand,when the current value detected from the current detecting unit 102 isthe same as or smaller than the stand current value, and the estimatedstroke value is greater than the stroke reference value, the controlunit 104 outputs a control signal for shortening the turn-on period ofthe Tr to the Tr and thus decreases the stroke voltage supplied to theinterior motor of the reciprocating compressor 200. That is, a stroke ofthe compressor 200 is varied by increasing or decreasing the strokevoltage (S25-S27).

Herein, the standard current value is preset by a user, and means acurrent value, which should be applied to the motor so that the interiormotor of the compressor 200 is normally operated. That is, the standardcurrent value is set by previously measuring a current value applied tothe interior motor of the compressor when the compressor is normallyoperated, and then storing the measured value.

Accordingly, in the present invention, a damage of the compressor 200,which is caused by an overload (overcurrent), can be prevented withoutthe OLP and the PTC thermistor, and the compressor 200 can be controlledclosely.

As so far described, in the present invention, a damage of a compressor,which is caused by the overcurrent, can be prevented by cutting offpower applied to the interior motor of the compressor when a compressoris operated, or by applying power to the interior motor of thecompressor, without using the OLP and the PTC thermistor.

Also, in the present invention, since the conventional OLP and the PTCthermistor is not used, but the operation control apparatus forcontrolling a stroke of the compressor is used, the stroke can becontrolling closely, and a production cost of the compressor can bereduced.

Also, in the present invention, a compressor can be miniaturized bycontrolling an operation of the compressor through the current controldevice without using the conventional OLP and the PTC thermistor.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover modifications and variationsof this invention provided they come within the scope of the appendedclaims and their equivalents.

1. An operation control apparatus for a compressor comprising: a strokeestimating unit for estimating a stroke of the compressor on the basisof a current and a voltage applied to an interior motor of thecompressor and a motor constant of the interior motor; a control unitfor generating a control signal for varying a stroke of the compressoron the basis of the estimated stroke value and a preset stroke referencevalue; and a current control means for varying a stroke voltage appliedto the interior motor of the compressor in accordance with the controlsignal.
 2. The apparatus of claim 1, wherein an OLP (Over LoadProtector) and/or a PTC thermistor (Positive Temperature Coefficientthermistor) are not used for the operation control apparatus.
 3. Theapparatus of claim 1, wherein the control unit outputs the controlsignal for increasing the stroke voltage applied to the compressor whenthe compressor is initially driven, to the current control means.
 4. Theapparatus for claim 1, wherein, when the estimated stroke value issmaller than the stroke reference value, the control unit increases avoltage applied to the compressor by lengthening an on/off period of thecurrent control means, and, when the estimated stroke value is greaterthan the stroke reference value, the control unit decreases a voltageapplied to the compressor by shortening the on/off period of the currentcontrol means.
 5. An operation control apparatus for a compressorcomprising: detecting means for detecting a current and a voltage whichare applied to a compressor; a storing means for presetting a standardcurrent value for preventing an overcurrent generated when thecompressor initially starts, and storing the set standard current value;a comparing means for comparing the detected current value and thestandard current value, and outputting a comparing signal correspondingto the comparing result; and a control means for cutting off a currentapplied to the compressor by turning off a current control meansinstalled at the compressor by the comparing result, or for controllinga stroke voltage applied to the compressor by turning on/off the currentcontrol means at a certain period.
 6. The apparatus of claim 5, whereinthe current control means is one of a triac, a GTO transistor (gateturn-off transistor), an IGBT (Insulated Gate bipolar Transistor), abipolar transistor and a relay.
 7. The apparatus of claim 5, wherein thecompressor is installed at a refrigerator.
 8. The apparatus of claim 5,wherein the control means cuts off a current applied to the compressorby turning off the current control means when the detected current valueis greater than the standard current value; and compares the strokevalue estimated based on the detected voltage value, the detectedcurrent value and a motor constant of an interior motor of thecompressor with the preset stroke reference value, and then varies astroke of the compressor on the basis of the comparing result when thedetected current value is smaller than the standard current value. 9.The apparatus of claim 5, wherein an OLP (Over Load Protector) and/or aPTC thermistor (Positive Temperature Coefficient thermistor) are notused for the operation control apparatus.
 10. A method for controllingan operation of a compressor comprising the steps of; detecting acurrent and a voltage applied to the compressor; estimating a stroke ofthe compressor on the basis of the detected values of the current andthe voltage and a motor constant of an interior motor of the compressor;when the estimated stroke value is smaller than a preset strokereference value, increasing a voltage applied to the compressor bylengthening an on/off period of a current control means installed at thecompressor, and when the estimated stroke value is greater than a presetstroke reference value, decreasing a voltage applied to the compressorby shortening the on/off period of the current control means.
 11. Amethod for controlling an operation of a compressor comprising:detecting a current applied to the compressor; comparing the detectedcurrent value and a preset standard current value; cutting off a currentapplied to the compressor by turning off a current control meansinstalled at the compressor when the detected current value is greaterthan the standard current value; and when the detected current value isthe same as or smaller than the standard current value, estimating astroke of the compressor, and controlling a stroke voltage applied tothe compressor by turning on/off the current control means at a certainperiod on the basis of the estimated value and the preset strokestandard current value.